Many critical electrically powered systems include one or more battery backup units that provide backup power to the system in the event of a loss of utility power. Battery backup units, however, can degrade over time to a point of not being capable of providing adequate backup power to the system in the event of loss of utility power. Moreover, respective cells of a battery backup unit may degrade at different rates, which may lead to erratic or irregular occasions for replacement that correspond to associated costs in upkeep and problems in predictability or reliability.